EP0447811B1 - Flow monitoring and measuring device - Google Patents

Abstract

The invention relates to a flow-indicating and -measuring device, having an impeller rotatably mounted in an essentially circular-cylindrical flow chamber, possessing an inlet channel and an outlet channel, belonging to a flow housing. So that such an indicating and measuring device can be used with high measuring accuracy for a wide measuring range without calibration, according to the invention a nozzle disc (14) having a nozzle bore or nozzle mouth (15) of predetermined cross-section can be inserted, for example screwed, exchangeably into the inlet channel (1) and/or the outlet channel (2), and the diameter D (in mm) of the nozzle bore (15) can be so fixed as a function of the lower limit R1 (in litres of water per minute) of the measuring range that the diameter D increases with an increase of the ratio V = R1/D, V assuming a value of approximately 0.075 litres of water/mm.min when the diameter D is approximately 1.25 mm and assuming a value of approximately 0.3 litres of water/mm.min when the diameter is approximately 20 mm. <IMAGE>

Description

The invention relates to a flow indicator or Flow meter according to the preamble of claim 1.

Such flow indicators or flow meters are on known. They either provide an immediate flow indication in that the rotating with current Impeller at the ends of the blades with alternately poled Magnet is equipped, which in a stationary take-up coil Trigger voltage pulses. This electrical Pulses can be amplified in an electronic circuit and are counted, from which the flow rate or Determine the flow and display it in liters or Liters / minute by means of LEDs. Such For example, vane wheel flow indicators or measuring devices have the advantage over some variable area flowmeters an almost viscosity-independent display or measurement result. The known devices of this type, such as that in the DE 37 33 862 A1 shown and described, however, are each only designed for a certain flow rate range and must be completely replaced when changing the measuring range and / or recalibrated, which takes time and effort is connected and also represents a source of error and thus the measuring accuracy may be adversely affected.

Proceeding from this, it is an object of the present invention a flow indicator or flow meter of the beginning mentioned type so that it can be used without calibration equally high accuracy for at least one other evaluation area can be used.

This object is achieved according to the invention with a device Claim 1 solved. The nozzle disc is therefore simple Way against another nozzle disc with a matching one Interchangeable nozzle bore diameter, causing the device to different measuring ranges with high measuring accuracy can be interpreted.

A particularly high measuring accuracy for further measuring ranges is achieved in an advantageous embodiment of the invention in that the nozzle bore diameter of the nozzle disks is graded in fine steps depending on the ratio V = R ₁ / D, as indicated in the characterizing part of claim 2.

In the known devices, which have magnets of changing polarity in the vanes of the impeller an even number of blades is required. However, this can be undesirable Lead resonances and starting difficulties of the impeller. The resonances lead to a considerable one Stress the storage of the impeller, which is increased by the fact that by the Magnetic inertial mass of the impeller in a relatively large radial distance from the Axis of rotation lies. In an advantageous development of the invention it is therefore provided that the impeller has an odd number of wings.

To further reduce the flow resistance of the new device. are the center of the Inlet opening of the inlet channel of the flow chamber and outlet opening of the outlet channel of the flow chamber preferably at a circumferential distance of only about 180 ° or less, preferably in a circumferential distance between 180 ° and 160 °.

In a further embodiment of the invention, the inlet duct and outlet duct are preferably located with housing openings lying on opposite end faces of the flow housing in Flow connection.

Starting problems of the impeller can be avoided with certainty if at least the inlet channel obliquely to the radial direction, preferably at an angle between 10 ° and 80 ° to Radial direction, opens into the outer surface of the flow chamber. This makes it more compact Design ensures that the flow is certainly with a component perpendicular to a wing impeller strikes this wing.

The outlet channel can also be inclined to the radial direction, preferably at an angle between 10 ° and 80 ° to the radial direction, away from the outer surface of the flow chamber equipped device, depending on the space available, the fluid to be measured can either be from one or the other side from the flow chamber.

In order to achieve favorable flow conditions, the invention also proposes that Housing openings for the inlet channel and / or outlet channel centrally in the opposite end faces of the flow housing.

The flow direction determined by the central longitudinal axis of the nozzle bore preferably leads in the used, e.g. screwed position of the nozzle disc regardless of the direction of Inlet channel obliquely to the radial direction, preferably at an angle between 10 ° and 80 ° to Radial direction, in the (imaginary) surface of the flow chamber, so that the impeller starts up is always guaranteed.

It is further proposed that in a further embodiment of the invention the central longitudinal axis of the Inlet channel or the nozzle bore on the radially outer end portions of the passing wing of the To align the impeller to exert a large torque on the impeller.

Radially within the radially outer end portions of the blades, the blades of the impeller can be broken, causing the mass of the impeller and the resistance to twisting within the filled flow chamber can be reduced.

The radially outer end sections of the vanes of the impeller have the smallest possible distance in any case less than one millimeter, preferably less than 0.5 mm, from the outer surface of the flow chamber, so that they almost seal. As a result, the counting or measuring accuracy due to low leakage elevated.

So that the device is not only used as a flow indicator, but also as a flow measuring device the impeller has a number of magnets arranged at a circumferential distance from one another, Ferrite cores or the like. Impulse-generating elements. In contrast to the prior art, at which the magnets are provided at the radially outer ends of the wings are according to the invention the pulse-generating elements preferably in the vicinity of the axis of the impeller. Hereby the moment of inertia of the impeller is considerably reduced. This reduces the number of bearings charged. In addition, the magnets are not provided in the wings or their ends, so that despite the odd number of wings an even number of magnets with alternating polarity for the Interaction with a stationary Hall sensor or with ferrite cores for interaction with a stationary coil can be provided.

The impulsive elements are preferably combined in a sector disk, wherein an impulse element is arranged in each sector.

The sector disk can be part of the hub of the impeller or connected to it in a rotationally fixed manner.

It is also advantageous if the pulse-generating elements are adjacent to a flat side wall of the flow housing are arranged, namely adjacent to that side wall, behind which the Hall sensor, the coil or a proximity sensor are provided for generating the electrical pulses is. In this way, relatively large electrical impulses are obtained.

The impeller can be arranged on a rotationally fixed axis. However, one is required for this adequate lubrication. It is more advantageous if, according to the invention, the impeller rotates on a Shaft is received, which in the two opposite flat side walls of the flow housing is rotatably mounted.

According to a further feature of the invention, the bearing for the shaft is changed from one in one Side wall axially fixed and one in the other side wall, preferably from the outside, axially adjustable bearing element formed. In this way, the impeller can be assembled quickly and safely guaranteed with long-term functionality.

The simple assembly also serves if at least one of the flat side walls of the Flow housing is at least partially formed by a detachably fastened housing cover, as is known in itself.

At least one of the flat side walls that are parallel to the impeller and preferably the bearing elements for the impeller, or at least one of the housing covers, which the have the same position and function, is made of transparent material, so that there is a Malfunction rotating impeller is visible from the outside and therefore a flow indicator without electronic Circuit is given. If both side walls and the housing cover are transparent, both can Sides can be optically determined whether in the line in which the flow housing is switched on is a current or not.

A reliable sealing of the flow housing can be obtained with simple installation when protrude the housing cover with a shoulder in a recess in the side walls and there by means of a sealing ring are radially sealed.

The flow housing according to the invention can have connecting sleeves for the inlet channel or the outlet channel have either a pipe connection via thread or via flange. To one allow easy installation of a pipe connection via thread, the are at their outer end e.g. with an internal thread connection sleeves with a sleeve section by means of a sealing ring in a threadless bore of the inlet channel or outlet channel inserted sealingly and the sleeve section has a groove with a round groove base which is matched by a section of at least one Groove formed from the outside of the housing bore is opposite the threadless bore. In the respective housing bore is then e.g. Safety pin designed as a set screw. In this way, the connection sleeves become axially immovable, but rotatable on the flow housing held. whereby a screw connection to the connecting line is produced in a simple manner can be. Even during operation of the device, the connection sleeves can be relative to the Flow housing can be moved without the tightness of the connecting sleeves is impaired. A further constructive and functional advantage is hereby achieved.

In order to obtain a device that is as compact as possible, the flow housing is shown in FIG a recess of a device housing fitted, which is used to hold the electronic circuit is determined.

The outer shape of the flow housing is preferably essentially cuboid trained and preferably aligned in the position of the flow housing inserted into the device housing the exposed outer surfaces of the flow housing with the adjacent outer surfaces of the Device housing. This creates a compact overall device with merging outer surfaces created. Should only be a flow display. can the flow housing with impeller and Connection sleeves can be used independently. However, if the device is to (also) serve as a flow meter, it is thus integrated into the device housing of the overall housing. This integration is also retrospective possible if from a purely visual display of a flow a measurement of the flow rate or the flow through the magnets, ferrites or the like. Impulse-generating elements and an electronic Switching take place and a display via LEDs and / or digital signals is to take place.

When integrating the flow housing into the device housing, it is proposed in particular that that the outer surface of the one side wall of the flow housing with the front The outer surface of the device housing is aligned. The relevant side wall of the flow housing or the housing cover forming them are preferably made of transparent material, so that the Device not only for flow rate measurement or flow measurement, but also for mere visual Flow indicator can be used.

Since the electronic circuit should not be exposed to temperatures above 100 ° C, that too measuring fluids but partly can have higher temperatures when the flow housing is integrated in the device housing further proposed that the flow housing in the Device housing used position is thermally insulated from the device housing, for example by intermediate layer of thermally insulating plates.

In order to be able to easily switch the device according to the invention to different measuring ranges, can the frontal outer surface of the device housing can be equipped with a replaceable scale field plate.

A simple manufacture and assembly of the device is ensured by the fact that the device housing is designed as a section of an extruded hollow profile.

To prevent the maximum temperature in the device housing from being exceeded, the outer surfaces of the device housing can be profiled, e.g. be designed with ribs or grooves, which run in the longitudinal direction of the extruded profile, so that the individual device housings are simple from the continuous hollow profile strand can be cut.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing.

Fig. 1

eine Ausführungsform des erfindungsgemäßen Gerätes im Vertikalschnitt A-B von Fig. 3,

Fig. 2

das Gerät gemäß Fig. 1 in einem Horizontalschnitt C-D von Fig. 3,

Fig. 3

einen Vertikalschnitt E-F des erfindungsgemäßen Gerätes gemäß Fig. 2,

Fig. 4

eine Schnittdarstellung entsprechend Fig. 1 einer anderen Ausführungsform eines erfindungsgemäßen Gerätes (Schnitt A-B von Fig. 6),

Fig. 5

einen Horizontalschnitt C-D gemäß Fig. 6 des erfindungsgemäßen Gerätes von Fig. 4,

Fig. 6

einen Vertikalschnitt C-D von Fig. 5 des erfindungsgemäßen Gerätes gemäß Fig. 4,

Fig. 7

ein als Strömungsmeßgerät ausgebildetes Gerät im Vertikalschnitt A-B von Fig. 9,

Fig. 8

einen Horizontalschnitt E-F von Fig. 9 des erfindungsgmäßen Gerätes gemäß Fig. 7,

Fig. 9

einen Vertikalschnitt E-F von Fig. 8 des erfindungsgemäßen Gerätes von Fig. 7,

Fig. 10

einen Vertikalschnitt A-B entsprechend Fig. 7 für eine andere Ausführungsform eines erfindunsgemäßen, als Strömungsmeßgerät ausgebildeten Gerätes,

Fig. 11

einen Horizontalschnitt C-D von Fig. 12 eines erfindungsgemäßen Gerätes von Fig. 10,

Fig. 12

einen Vertikalschnitt E-F von Fig. 11 eines erfindungsgemäßen Gerätes nach Fig. 10, und

Fig. 13

eine Schrägansicht eines erfindungsgemäßen Strömungsanzeige- und - meßgerätes, bei welchem das Strömungsgehäuse in eine Aussparung des Geräteg ehäuses zur Schaffung eines Kompaktgerätes eingesetzt ist.

Show it:

Fig. 1

1 shows an embodiment of the device according to the invention in vertical section AB from FIG. 3,

Fig. 2

1 in a horizontal section CD of FIG. 3,

Fig. 3

3 shows a vertical section EF of the device according to the invention according to FIG. 2,

Fig. 4

2 shows a sectional view corresponding to FIG. 1 of another embodiment of a device according to the invention (section AB from FIG. 6),

Fig. 5

6 a horizontal section CD according to FIG. 6 of the device according to the invention from FIG. 4,

Fig. 6

5 shows a vertical section CD from FIG. 5 of the device according to the invention according to FIG. 4,

Fig. 7

a device designed as a flow meter in vertical section AB of FIG. 9,

Fig. 8

9 shows a horizontal section EF from FIG. 9 of the device according to the invention according to FIG. 7,

Fig. 9

8 shows a vertical section EF from FIG. 8 of the device according to the invention from FIG. 7,

Fig. 10

7 shows a vertical section AB corresponding to FIG. 7 for another embodiment of a device according to the invention, designed as a flow measuring device,

Fig. 11

12 shows a horizontal section CD from FIG. 12 of an apparatus according to the invention from FIG. 10,

Fig. 12

a vertical section EF of Fig. 11 of an inventive device according to Fig. 10, and

Fig. 13

an oblique view of a flow display and measuring device according to the invention, in which the flow housing is inserted into a recess of the device housing to create a compact device.

1-3 illustrate a flow display device according to the invention, consisting of a Flow housing 4 with a substantially circular cylindrical flow chamber 3, in which a Impeller 5 is rotatably mounted. The flow chamber 3 is with an inlet channel 1 and Outlet duct 2 equipped. The centers of the inlet opening 7 of the inlet channel 1 of the flow chamber 3 and the outlet opening 8 of the outlet channel 2 of the flow chamber 3 are located at a circumferential distance from each other, which is less than 180 °. Inlet channel 1 and outlet channel 2 are on each other opposite end faces 12, 13 of the flow housing 4, housing openings 9, 10 in Flow connection. The housing openings 9, 10 for inlet channel 1 and outlet channel 2 are in the center the opposite end faces 12, 13 of the flow housing 4. From the housing opening 9 leads the inlet channel 1 obliquely to the radial direction by means of the inlet opening 7 in the lateral surface 11 of the Flow channel 3. The outlet channel 2 leads obliquely to the radial direction from the outlet opening 8 from the Shell surface 11 of the flow chamber 3 away. In the inlet channel 1 equipped with an internal thread a nozzle disk 14 equipped with an external thread is screwed in, which has a nozzle bore 15 predetermined cross-section. The nozzle disk 14 has two engagement openings on the outside for a turning tool. The central longitudinal axis 16 of the nozzle bore 15 is like that of the inlet duct 1 even on the radially outer end portions 17 of the wing 6 passing by the inlet opening 7 Impeller 5 directed. The vanes 6 of the impeller 5 can, as indicated in Fig. 1, too be broken. The radially outer end portions 17 of the blades 6 of the impeller 5 hold one the smallest possible distance from the lateral surface 11 of the flow chamber 3, so that a possible low fluid leakage takes place on the lateral surface 11.

The impeller 5 is rotatably received on a shaft 23 which in the two each other opposite flat side walls 22, 24 of the flow housing 4 is rotatably mounted. The Bearing for the shaft 23 is axially fixed in a side wall 22 and one in the another side wall 24 from the outside axially adjustable bearing element 25, 26 is formed. Both flat-sided Side walls 22, 24 of the flow housing 4 can each be removed by means of screws 55 attached housing cover 27, 28 formed. The housing cover 27, 28 can be made of transparent material consist. The housing cover 27, 28 protrude with an extension 51, 52, which the bearing elements 25, 26 for receive the shaft 23 of the impeller 5 into a recess in the side walls 22, 24. There are the approaches 51, 52 sealed radially against the flow housing 4 by means of a sealing ring 53, 54.

Inlet duct 1 and outlet duct 2 are provided with connecting sleeves 29, 30. The connecting sleeves 29, 30 are with a sleeve section 31, 32 by means of sealing ring 33 in a non-threaded bore of Inlet channel 1 and outlet channel 2 used sealing. The respective sleeve section 31, 32 has one Groove 34 with a round groove base, the two corresponding ones, each from a section two from the outside accessible housing bores 35 formed recesses 36 of the unthreaded bore of the inlet channel 1 or the outlet channel 2 is opposite. In the housing bores 35 is designed as a threaded pin Locking pin 37 inserted. In this way, the connecting sleeves 29, 30 are fixed axially, however rotatable relative to the flow housing 4.

The flow display device according to FIGS. 4-6 differs from that in FIGS 1 - 3 essentially only in that the connecting sleeves 29 ', 30' for inlet channel 1 and outlet channel 2 do not have an internal thread 56 for a pipe screw connection, but a flange 57, 58 for a Flange connection. In addition, the connection sleeves 29 ', 30' are in this case with the flow housing 4 welded.

The embodiment of the device according to FIGS. 7-9 is similar to that from FIGS. 1-3 Fig. 7-9, the device is equipped as a flow meter, which is not just an optical Flow display due to the transparent material of the one housing cover 27 (a housing cover 28 is missing here), but also an electrical measurement display for the flow rate or Execution. For this purpose, the impeller 5 has a number of circumferentially spaced apart arranged magnets, ferrite cores or the like. Impulse-generating elements 18, which in immediate Neighborhood to the axis 19 of the impeller 5 in a e.g. plastic sector disk 20 are summarized and included, with an impulse element 18 in each sector is arranged. The sector disk 20 forms part of the hub 21 of the impeller 5 Elements 18 are immediately adjacent to the flat side wall 22 of the flow housing 4 arranged, on the outside there is a Hall generator, not shown, a coil, not shown or a proximity switching element, not shown, for generating an electrical voltage or Current signal is arranged. The flow housing 4 can, as can be seen from FIGS. 8 and 13, by means of Screws 59 can be fixed in the recess 38 of a device housing 39.

The embodiment of a device according to the invention according to FIGS. 10-12 corresponds in essential to that of FIGS. 7-9. Here, however, are again those for a threaded connection provided connecting sleeves 29, 30 replaced by connecting sleeves 29 'and 30' with flanges which with the Flow housing 4 are welded, similar to the embodiment of FIGS. 4-6 Structure identical.

Fig. 13 shows an oblique view of an overall device with flow housing 4, which in the recess 38 of the device housing 39 is fitted and integrated with it into a compact overall shape. The Connection sleeves 29, 30 and 29 ', 30' are not shown. The housing cover 27 consists of transparent Material so that the device as both a flow indicator and a flow meter can be used with the help of the electronic circuit housed in the device housing 39 is. The recess 38 of the device housing 39 corresponds to the outer shape of the flow housing 4 cuboid in such a way that the exposed outer surfaces 40 - 43 of the flow housing 4 with the adjacent outer surfaces 44 - 47 of the device housing 39 are aligned. The outer surface 40 of one flat side wall 22 of the flow housing 4 is particularly aligned with the frontal outer surface 44 of the device housing 39. The flow housing 4 is also opposite the device housing 39 thermally insulated by placing heat insulating plates between the flow housing 4 and the device housing 39 are laid. The frontal outer surface 44 of the device housing 39 is interchangeable Scale field plate 50 equipped, from which the analog or digital display of the flow rate or the flow e.g. by means of LEDs. Here, for example, additional functions such as Reaching or exceeding a predetermined limit value, the operating state (on / off) of the device, the signal range (in mA) are displayed, as well as actuators for setting the measuring range u. Like. Be provided.

The device housing 39 is designed as a section of an extruded hollow profile and its outer surfaces 40 - 49 are profiled, e.g. with ribs or grooves which run in the longitudinal direction of the hollow profile strand.

Reference symbol list:

1

Inlet duct

2nd

Exhaust duct

3rd

Flow chamber

4th

Flow housing

5

Impeller

6

wing

7

Inlet opening

8th

Outlet opening

9

Housing opening

10th

Housing opening

11

Lateral surface

12th

Face

13

Face

14

Nozzle disc

15

Nozzle bore

16

Central longitudinal axis

17th

End sections

18th

stimulating elements

19th

axis

20th

Sector disk

21

hub

22

Side wall

23

wave

24th

Side wall

25th

Bearing element

26

Bearing element

27

Housing cover

28

Housing cover

29, 29 '

Connection sleeves

30, 30 '

Connection sleeves

31

Sleeve section

32

Sleeve section

33

Sealing ring

34

puncture

35

Housing bore

36

puncture

37

Locking pin

38

Recess

39

Device housing

40

Outside surface

41

Outside surface

42

Outside surface

43

Outside surface

44

Outside surface

45

Outside surface

46

Outside surface

47

Outside surface

48

Outside surface

49

Outside surface

50

Scale field plate

51

approach

52

approach

53

Sealing ring

54

Sealing ring

55

Screws

56

inner thread

57

flange

58

flange

59

Screws

Claims (30)

1. Flow monitoring and measuring device with a impeller (5) mounted rotatably in a flow chamber (3) of a flow housing (4), where the said chamber has an essentially circular cylindrical shape with an inlet duct (1) and an outlet duct (2), and with interchangeable nozzle plates (14), one of which with a nozzle bore or opening (15) of predetermined cross section is inserted in the inlet duct (1) and to set another evaluation range, i.e. monitoring or measurement range, is held replaceably against a second nozzle plate (14) with a second predetermined cross section of nozzle bore or opening (15), characterised in that the diameter D in mm of the nozzle bore or opening (15) of the second nozzle plate (14) is such that ratio V = R₁/D, where R₁ in litres water/min is the flow which represents the lower limit of the evaluation range concerned, increases with the increase in diameter D, i.e. the lower limit R₁ as a function of diameter D increases more strongly than the diameter D itself, where if the diameter D is approximately 1.25 mm and R₁ approximately 0.09 litres water/min, the ratio has a value of 0.075 litres water/min x mm and if diameter D is approximately 20 mm and R₁ approximately 6 litres water/min, a value of approximately 0.3 litres water/min x mm.
2. Device according to claim 1, characterised in that the diameter D can be set as a function of the lower limit R₁ of the measurement range such that the following ratio exists between diameter D and ratio V for interchangeable nozzle plates: R₁ (litres water/min) D (mm) V (litres water/mm min) ^∼0.09 1.25 ^∼0.075 ^∼0.17 1.90 ^∼ 0.090 ^∼0.38 2.55 ^∼0.15 ^∼1.52 7.60 ^∼ 0.20 ^∼ 2.79 12.70 ^∼0.22 ^∼ 3.81 15.25 ^∼ 0.25 ^∼ 5.72 19.05 ^∼0.30
3. Device according to claim 1 or 2, characterised in the impeller (5) has an odd number of vanes (6).
4. Device according to any of claims 1 to 3, characterised in that the centre point of the inlet opening (7) of the inlet duct (1) of the flow chamber (3) and the outlet opening (8) of the outlet duct (2) of the flow chamber (3) lie at a peripheral interval of approximately 180° or less, preferably at a peripheral interval of between 180° and 160°.
5. Device according to any of claims 1 to 4, characterised in that the inlet channel (1) and the outlet channel (2) have a flow connection with housing openings (9, 10) lying on opposite faces (12, 13) of the flow housing (4).
6. Device according to any of claims 1 to 5, characterised in that at least the inlet duct (1) opens obliquely to the radial direction, preferably at an angle of between 10° and 80° to the radial direction, in the generated surface (11) of the flow chamber (3).
7. Device according to any of claims 1 to 6, characterised in that the outlet duct (2) runs obliquely to the radial direction, preferably at an angle of between 10° and 80° to the radial direction, away from the generated surface (11) of the flow chamber (3).
8. Device according to any of claims 1 to 7, characterised in that the housing openings (9, 10) for the inlet duct (1) and/or outlet duct (2) lie centrally in the opposite faces (12, 13) of the flow housing (4).
9. Device according to any of claims 1 to 8, characterised in that the flow direction determined by the central longitudinal axis (16) of the nozzle bore (15), when the nozzle plate (14) is inserted e.g. screwed in, runs oblique to the radial direction, preferably at an angle of between 10° and 80° to the radial direction in the (theoretical) generated surface (11) of the flow chamber (3).
10. Device according to any of claims 1 to 9, characterised in that the centre longitudinal axis (16) of the inlet duct (1) or the nozzle bore (15) is aligned to the radial outer end sections (17) of the passing vane (6) of the impeller (5).
11. Device according to any of claims 1 to 10, characterised in that the vanes (6) of the impeller (5) are perforated.
12. Device according to any of claims 1 to 11, characterised in that the radial outer end sections (17) of the vane (6) of the impeller (5) have a small distance, in any case less than 1 mm, preferably less than 0.5 mm, from the generated surface (11) of the flow chamber (3).
13. Device according to any of claims 1 to 12, characterised-in that the impeller (5) has a number of magnets, ferrite cores or similar pulse-emitting elements arranged at peripheral intervals.
14. Device according to claim 13, characterised in that the pulse-emitting elements (18) are arranged adjacent to the axis (19) of the impeller (5).
15. Device according to claim 13 or 14, characterised in that the pulse-emitting elements (18) are combined in a sector plate (20), where one pulse-emitting element (18) is arranged in each sector.
16. Device according to claim 15, characterised in that the sector plate (20) forms part of the hub (21) of the impeller (5) or is rotationally firmly connected to this.
17. Device according to any of claims 13 to 16, characterised in that the pulse-emitting elements (18) are arranged adjacent to a flat side wall (12) of the flow housing (4).
18. Device according to any of claims 1 to 17, characterised in that the impeller (5) is held rotationally firmly on a shaft (21) which is mounted rotatably in the two opposing flat side walls (22, 24) of the flow housing (4).
19. Device according to claim 18, characterised in that the bearing for the shaft (23) is formed by a bearing element (25, 26) placed axially fixed in a side wall (22) and axially adjustable preferably from the outside, in another side wall (24).
20. Device according to any of claims 1 to 19, characterised in that at least one of the flat side walls (22, 24) of the flow housing (4) is formed at least partly by a removably attached housing cover (27, 28).
21. Device according to any of claims 1 to 20, characterised in that at least one of the flat side walls (22, 24) or at least one of the housing covers (27, 28) is made of transparent material.
22. Device according to claim 20 or 21, characterised in that the housing covers (27, 28) project with an attachment (51, 52) in a recess of the side wall (22, 24) and are there sealed radially by means of a sealing ring (53, 54).
23. Device according to any of claims 1 to 22, with connecting sleeves (29, 30) for the inlet duct (1) and the outlet duct (2) characterised in that the connecting sleeves (29, 30) are inserted with a sleeve section (31, 32) in an unthreaded bore of the inlet duct (1) or the outlet duct (2) and sealed by means of a sealing ring (33) and that the sleeve section (31, 32) has a notch (34) with a round groove base which lies opposite a corresponding notch (36) in the unthreaded bore formed by a section of at least one housing bore (35) accessible from the outside, and that a locking pin (37) formed for example as a threaded pin is inserted in the housing bore (35) concerned.
24. Device according to any of claims 1 to 23, characterised in that the flow housing (4) is fitted in a recess (38) of a device housing (39).
25. Device according to claim 24, characterised in that the outer shape of the flow housing (4) is essentially cuboid and when the flow housing (4) is inserted in the device housing (39), the exposed outer surfaces (40 - 43) of the flow housing (4) are aligned with the adjacent outer surfaces (44 - 47) of the device housing (39).
26. Device according to claim 24 or 25, characterised in that the outer surface (40) of one flat side wall (22) of the flow housing (4) is aligned with the front outer surface (44) of the device housing (39).
27. Device according to any of claims 24 to 26, characterised in that the flow housing (4), when inserted in the device housing (39), is thermally insulated from the device housing (39).
28. Device according to any of claims 24 to 27, characterised in that the front outer surface (44) of the device housing (39) is fitted with a replaceable scale field plate (50).
29. Device according to any of claims 24 to 28, characterised in that the device housing (39) is formed as section of the hollow extrusion profile.
30. Device according to any of claims 24 to 29, characterised in that the outer surfaces (40 - 49) of the device housing (39) are profiled, e.g. fitted with ribs or grooves.

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